This is the 14094th most frequent Russian word.
окон
"Окон" is the genitive plural form of "окно," which means "windows" (of windows).
The word 'окон' is used in its plural genitive form, referring to the general mentioning of multiple windows.
В комнате было много светлых окон.
There were many bright windows in the room.
Here, 'окон' is in its plural genitive form to indicate possession or relation to the description of the windows.
Мы посмотрели вид из окон на верхнем этаже.
We looked at the view from the windows on the top floor.
In this sentence, 'окон' is again in the plural genitive form used after 'без' (without), a preposition that governs the genitive case.